The Mesoamerican Reef – stretching 700 miles from the Yucatán Peninsula down to the Bay Islands of Honduras – is the largest coral reef in the Western Hemisphere and the second largest barrier reef in the world. It's made up of an array of corals and is home to more than 500 species of fish, including the mammoth whale shark, the largest fish in the world.

Global conservation organisations such as WWF can't work everywhere, so we need to find the areas that are of strategic importance. And the reef is just that. More than a decade ago our work in the Mesoamerican Reef focused on marine protected areas, like overfishing, urban sewage and tourism – as these were seen as the key threats to the reef. But as we started to learn more, our focus shifted.

In the late 1990s several journal articles suggested that soil erosion and agro-chemical run-off can cause coral bleaching to occur at lower temperatures than it would otherwise. We knew the reef had been seriously affected by coral bleaching, so we started to investigate the impact of agri-business in the surrounding watershed. What was the impact on the reef of the local banana, pineapple, citrus, palm oil and sugar operations?

Science and research through collaboration would tell us. We collected samples from more than a dozen different species, such as sea grass, invertebrates, herbivores, corals, and carnivores like parrot fish, grouper and barracuda to see if pesticide residues had accumulated in their tissues. Then we analysed a list of agro-chemicals used on target crops in Belize and Honduras provided by Earth University in Costa Rica.

The most modern lab in the region, in Belize, analysed the samples to produce astounding results. They suggested that every species had accumulated high levels of agro-chemicals, but the chemicals were different. Seagrass and corals accumulated herbicides. Carnivores tended to accumulate a broader range and higher levels of chemicals. Some chemicals found had not been used for 20 years! But we also learned that the newer chemicals, which were supposed to break down faster, were still bio-accumulating, meaning they were being absorbed into tissue.

The science helped us find a path to solution. We discovered that each manufacturing plant has its own signature, meaning it was possible to determine not only the chemicals, but also the plant they came from. Virtually all the chemicals that producers used were found in the reef organisms. We had found the smoking gun. The question was what to do about it.

We invited the agrochemical manufacturers (Dow, DuPont, Syngenta and CropLife) as well as the key multinational producer companies (Chiquita, Del Monte, Dole, and Fyffes) to meet and discuss the findings. As with any collaboration between unlikely allies, we encountered disagreement and concern. The companies were concerned about how the data was collected and analysed, and about how WWF would use it. So we started by focusing on what everyone agreed upon.

Together, we agreed to peer-review the sample collection and lab analysis methodologies over the next year (interestingly, the methodologies were officially adopted by New Zealand and the US, and in the latter case, used to evaluate contamination levels following Hurricane Katrina).

We agreed that it was important to evaluate the toxicity of the chemicals as a means to reduce soil erosion. Each company agreed to turn over its data on chemical usage, quantities, timing and methods of application to WWF, while WWF agreed to keep the information confidential. We agreed that we would eventually publish our findings in a peer-reviewed journal. Until then, all data would stay private until we had solutions to address the problem.

The project has changed the way agri-businesses manage banana, citrus, palm oil, pineapple and sugarcane production. By shifting the focus to mutually agreed results, each company was free to identify the best practices for its production system. To date, we have achieved a 50% reduction in overall pesticide toxicity and have targeted a 50% reduction in soil erosion by 2020.

Moreover, the project helped forge newfound trust and partnerships. Companies shared chemical, production and pesticide use data, and allowed WWF on their sites to measure soil erosion. Together we developed a "toxicity model" that enabled the companies to reduce the toxicity of chemicals while maintaining or even increasing production. In fact, a better understanding of these chemicals enabled companies to phase out expensive inputs, saving money and improving profitability.

All this could not have happened but for The Summit Foundation, a single donor with foresight to commit 10 years of funding to reduce soil erosion and agro-chemical toxicity – the two largest threats to the reef.

As this project shows, once we began to identify and measure the impacts, we improved overall performance. This is not only good for the ecosystems of the Mesoamerican Reef, it is good for the bottom line as well. While more work needs to be done to examine the impact of different chemicals on various reef organisms, we've proven that working collaboratively to solve shared problems is not only possible, but profitable.